SUBSTRUCTURE

SUBSTRUCTURE

1. Basements

   • Types of waterproofing system
     • Tanking
     • Integral
     • Drained
     • Influenced by number of factors
       • Nature of site
         • Access limitations?
         • Water table
         • proximity of existing structures
       • Building form
         • Depth of basement
         • Intended function eg car park
       • Legal issues
         • Rights of adjacent building owners
         • Health and sadety
   • Types of construction
     • Top down
       • Attempts to make use of permanent elements of construction works to provide rigidity and bracing against loadings from ground
       • Removes need for temporary support structures
       • Speedy and economical solution to formation of deep basements
       • Possible to commence formation of superstructure simultaneously with basement construction
     • Bottom up
       • Conventional method
       • Substructure and superstructure constructed sequentially
         • Bottom of substructure / lowest level of basement to top of the superstructure
       • Not feasible for gigantic projects with limited construction time and / or site constraints
   • Construction approaches
     • Open excavations
     • Excavation with temporary support
     • Excavation with permanent retaining walls formed prior to main excavation
       • Contiguous piles
       • Secant piles
       • Diaphragm walls

2. Foundations

   • Types
     • Piled
     • Strip
     • Pad
     • Raft
   • Soil types
     • Rock
     • Gravel and sands
     • Silts and clays
   • Functions
     • Safely transmit building loads to supporting strata, spreading them over a sufficient area to ensure that safe load bearing capacity of soil is not exceeded
   • Selection criteria
     • Ground conditions
       • Bearing capacity of ground
       • Depth of good strata
       • Ground level and gradients
     • Loads from building